The De Beers diamond mine is about one mile east from the Kimberley and in the central part of the city of Kimberley. In extent it is 958 feet east and west by 630 feet north and south and the original locations covered a surface equal to 622 claims or 13.72 acres. It was in this mine that Cecil Rhodes centered his interests, and from the nucleus he created there, forced the Kimberley interests to join the combination which finally embraced all the producing mines of South Africa at that time. The De Beers did not in the beginning, nor does it now, yield as many diamonds as the Kimberley, but the average quality is better, though not as good as those from the west end of the Kimberley, and the percentage of crystals which can be cut to jewels is larger. What the comparative output of the two mines of late years is, cannot be stated, as the returns are given together in the yearly statements of the company. In 1907 the combined output was less than that of the Wesselton or the Bultfontein, and the yield per load was but little better than either of the latter, the De Beers and Kimberley being .37 of a carat, the Wesselton .32 and the Bultfontein .33.
This mine is more liable t0 mud-rushes than the others of the Kimberley group. In 1902, 3 natives were killed and 6,989 feet of tunnels filled. The rock shaft at that time was down 1,784 feet, and the mine was worked from 11 levels at 40-ft. intervals, from 1,100 to 1,400 feet deep. 15,506 feet of new tunnels were cut. They had in sight above the 1,400-foot level, 1,289,500 loads of blue, and had, developed between that and the 1,720-foot level, 3,375,400 loads, a total of 4,664,900 loads in sight June 30, 1902. The cost of mining, de-positing and washing that year was 9S. 0.9d. per load, 7/10 of a penny per load more than the year previous and a little more than 2s. in excess of the Kimberley cost for the same year, which was 7s. 8.6d. per load.
In 1904 the rock shaft was down to 2,076 feet. In 1903 a tunnel was made around the mine in the hard rock under the shale, the same as in the Kimberley mine, t0 take up the water from the mud-rushes.
According to the annual reports published by the company, the combined yield percentage of the De Beers and Kimberley has declined steadily since the consolidation, the lowest averages in the history of the mines being those of 1907 and 1908, which were alike, .34 of a carat to the load. At the same time the cost per load has increased in the last ten years from 6s. 7.4d. in 1898 to 9S. 0.8d. in 1907.
The upper part of the De Beers mine was very poor. Some parts of it contained so few diamonds that it did not pay to work them. At two to three hundred feet, there was a marked improvement, which was maintained for a long time, and the fact probably gave rise to the general report, yet circulated with regard to the Kimberley group, that the blue is richer than the yellow was, the evidence of the annual reports showing the contrary, notwithstanding. The yellow ground of the Kimberley, from all accounts, contained more diamonds than any level of the blue under it, but in the other mines, both the yellow and the upper part of the blue were much poorer than the blue from about 200 to a thousand feet down. Below that, however, the yield per load appears to decline steadily with depth in all the mines.